1. Field of the Invention
This invention relates generally to sludge filtration systems for separating sludge solids from sludge liquids. More specifically, this invention relates to a filter for use in a container, designed for sludge filtration.
2. Description of the Related Art
The separation of sludge solids from sludge liquid is commonly practiced as an initial step in disposing of waste sludge. Generally, sludge includes, among other things, solid-liquid sludge and slurries such as sewage and industrial waste.
When treating sludge, it is desirable to separate the sludge liquids from the sludge solids for further treatment or recovery or disposal of the solids and liquids separately. A typical filtering system involves a container having filter systems arranged around the container walls and the container floor. Such systems commonly involve a metal, plastic, polypropylene or vinyl liquid-permeable filter mesh with openings such that particulates above a predetermined size do not pass through the filter. Due to the weight of sludge, such filtering systems include a support structure for the filter. The support structure is often comprised of a perforated plate or expanded metal plate. The filter media may be attached to the support structure by retention bars. An opening is typically provided intermediate the support structure and the container wall to provide for drainage of the sludge liquids. Due to the expense of disposable filters, it is desirable that the filter media be relatively strong.
Due to clogging effects of sludge containing small particulates, it is desirable that the filter media be removable for cleaning or replacement. As a result, prior art systems commonly use retainer bars to hold the filters and perforated plate in place. The retainer bars are typically bolted to the support structure. Removal of the filters for washing involves removing the retainer bars. Replacement of the filters involves aligning openings in the filters, perforated plate and support structure. For a large sludge container, such as a commonly practiced roll on roll off container, the weight of the plate and filters increases the difficulty of removal and replacement.
In a typical prior art sludge-dewatering container, the combined width of a support structure and filter is in the range of three inches (˜7.5 cm) to six inches (˜15 cm). Such prior art filters extend within the container and reduce the volume of sludge that can be processed by the container.
This Applicant's U.S. Pat. No. 5,681,460 teaches a selectively removable sludge filtration system that provides for retrofit into a container and separation of the sludge solids from the sludge liquids therein. This Applicant's U.S. Pat. No. 6,146,528 teaches removable filter assemblies for containers that enable thorough and efficient cleaning of the filter system. U.S. Pat. Nos. 4,929,353 and 5,589,081, issued to Harris, disclose basket-like filter structures. U.S. Pat. No. 4,929,353 teaches a filter that is placed in an existing structure, and is held in place with the weight of the sludge independent any fastening system. U.S. Pat. No. 5,589,081 teaches a removable filter that relies on the hydrostatic pressure created by the mass of sludge to force positive flow of sludge liquids out the drains found in the collection container.
Multiple layer structures for filtering are known in the art. Such filters often comprise a filter media with a support backing to provide lateral rigidity to the filter media. U.S. Pat. No. 5,776,567 to Schilling, et al. teaches a disposable multi-layer filter for separating solid and liquid wastes. U.S. Pat. No. 5,098,364 to Schilling, U.S. Pat. No. 5,110,005 to Schilling, U.S. Pat. No. 5,741,208 to Moak and U.S. Pat. No. 4,385,953 to Beck each teach liners for waste containers. U.S. Pat. No. 5,131,709 to Spica teaches a cargo bed liner system utilizing a plurality of grid-like modules.
It would be an improvement to the art to provide a re-usable sludge filter that does not require a perforated plate, expanded metal or like support structure and that optimizes use of the interior space of a container for sludge filtration.